1. Field of the Invention
The present invention relates to a packet communication system and its communication method, base station, and mobile station, and particularly, to a scheduling method of uplink and downlink packet communication in the packet communication system, specifically, to a scheduling method of a wireless base station for a wireless mobile station.
2. Description of the Related Art
In the packet communication of wireless mobile communication, it is common practice to schedule uplink communication (from a mobile station to a base station) using the reception quality of received uplink signal. In this case, a mobile station knows the presence of data to be transmitted. Thus, when there is data to be transmitted from the mobile station, the presence of data to be transmitted is notified with a reservation packet from the mobile station to a base station, the base station schedules the mobile station, from which the reservation packet has been received, based on the reception quality of received uplink signal, and notifies transmission permission, so that the mobile station transmits the data to the base station.
To the contrary in downlink communication (from a base station to a mobile station) for plural mobile stations, it is common practice to perform scheduling using the reception quality of received downlink signal. In this case, because a base station has data to be transmitted, if parameters (such as downlink reception quality) necessary for scheduling are obtained, the base station can schedule a mobile station and transmit the data.
An embodiment of such packet communication system is illustrated in FIG. 8 and FIG. 9. FIG. 8 is a configuration diagram of an embodiment of a base station in the related packet communication system, and FIG. 9 is a configuration diagram of a mobile station in the related packet communication system.
When uplink packet communication is performed, in a base station 51 illustrated in FIG. 8, an antenna unit 101 receives signals from a mobile station, not illustrated, and a signal receiving unit 102 separates the signals to signals of each mobile station and converts the signals to base band signals. Each of base band signals separated for each mobile station is inputted to a mobile station registration decision unit 103 and an uplink reception quality measurement unit 105.
The mobile station registration decision unit 103 determines the presence of reservation packet transmission from mobile stations, and notifies that the mobile station from which the reservation packet has been received has packet data to be transmitted to an information management unit 108 of each mobile station.
The uplink reception quality measurement unit 105 measures the uplink signal reception quality of each mobile station, and notifies the result to the information management unit 108 of each mobile station.
The information management unit 108 of each mobile station manages the presence of packet data and the uplink signal reception quality of each mobile station, and notifies information on the mobile station which has packet data to a scheduling processing unit 109.
The scheduling processing unit 109 obtains the priority of each mobile station from the uplink signal reception quality, selects the mobile station to which transmission permission is provided, and notifies the result to a signal transmission unit 110.
The signal transmission unit 110 generates signals for the mobile station notified from the scheduling processing unit 109, and transmits transmission permission signals through the antenna unit 101.
In a mobile station 61 illustrated in FIG. 9, a signal receiving unit 202 converts signals received by an antenna unit 201 to base band signals. The base band signals are inputted to a transmission permission signal decision unit 203.
The transmission permission signal decision unit 203 determines the presence of the transmission permission signals from the base station 51. An uplink packet data supply unit 208 notifies to a transmission data generation unit 206 when packet data exists.
The transmission data generation unit 206 notifies a signal transmission unit 207 to transmit a reservation packet when new packet data exists, and notifies the packet data from the uplink packet data supply unit 208 to the signal transmission unit 207 when the reservation packet has been transmitted and the transmission permission signals is notified from the base station 51.
The signal transmission unit 207 generates signals for the base station 51 from information notified from the transmission data generation unit 206, and transmits uplink signals through the antenna unit 201.
Next, when the downlink packet communication is performed, in the base station 51 illustrated in FIG. 8, the antenna unit 101 receives signals from the mobile station 61, and the signal receiving unit 102 separates the signals to signals of each mobile station 61 and converts the signals to base band signals. The base band signals of each mobile station 61 are inputted to the mobile station registration decision unit 103 and a downlink reception quality receiving unit 104.
The mobile station registration decision unit 103 determines from the presence of signals received from the mobile station 61 whether or not it is possible to transmit to the mobile station 61, and if possible, notifies the information to the information management unit 108 of each mobile station 61.
The downlink reception quality receiving unit 104 extracts the reception quality of downlink signal receiving included in signals received from the mobile station 61, and notifies it to the information management unit 108 of each mobile station 61.
The information management unit 108 of each mobile station 61 manages information whether or not it is possible to transmit to each mobile station 61, and the downlink signal reception quality, and notifies them to the scheduling processing unit 109. A downlink packet data supply unit 111 notifies the presence of data to be transmitted to each mobile station 61 to the scheduling processing unit 109.
The scheduling processing unit 109 schedules the mobile station 61 which has data to be transmitted based on the downlink signal reception quality, determines the mobile station 61 to which packet data is transmitted, and notifies information on the mobile station 61 to which packet data is transmitted and data to be transmitted to the signal transmission unit 110.
The signal transmission unit 110 generates signals for the mobile station 61 to which packet data is transmitted based on information notified from the scheduling processing unit 109, and transmits downlink signals through the antenna unit 101.
In the mobile station 61 illustrated in FIG. 9, the antenna unit 201 receives signals from the base station 51, and the signal receiving unit 202 converts the signals to base band signals. The base band signals are inputted to a receiving signal quality measurement unit 204. The receiving signal quality measurement unit 204 measures the reception quality of downlink signal receiving, and notifies the measurement result to the transmission data generation unit 206.
The transmission data generation unit 206 notifies the downlink signal reception quality to the signal transmission unit 207. The signal transmission unit 207 generates signals for the base station 51, and transmits uplink signals through the antenna unit 201.
When downlink packet is transmitted by the scheduling processing in the base station 51, the antenna unit 201 receives signals from the base station 51, the signal receiving unit 202 converts the signals to base band signals, then the downlink packet data receiving unit 205 receives downlink packet data.
One example of the inventions associated with the above related technology is disclosed in the Patent Document 1 (Japanese Patent Laid-Open No. 2005-341311).
On the other hand, the wireless packet communication system is disclosed which detects the location of a mobile station according to the distance between a mobile station and a base station, generates a function according to the location, and performs transmission scheduling of down link packet based on the function (refer to the Patent Document 2 (Japanese Patent Laid-Open No. 2002-171287 (paragraph: 0061 to 0063, 0067, and FIG. 2)). The Patent Document 2 describes that the function can be changed according to the date and the weather conditions.
However, when the scheduling is performed based on the signal reception quality in the packet communication of the related wireless mobile communication (including the invention disclosed in the Patent Document 1), there is such a problem that effective scheduling cannot be performed because time-dependent variation of signal propagation channel may be large due to environment, location, etc., and the propagation channel may change between the time when the reception quality is measured and the time when the scheduling is performed.
On the other hand, the invention disclosed in the Patent Document 2 is common to the present invention in that transmission scheduling of link packet is performed based on location of a mobile station. However, while the invention disclosed in the Patent Document 2 generates a function based on the transmission rate, the present invention generates coefficients based on the certainty of the reception quality, so that the configurations of both the inventions are very different each other in such a way that the weighting is performed using the location information.